Stone veneer walls:
This article describes how to troubleshoot & repair stone veneer walls on buildings: a stone "skin" placed over masonry or wood framing: the construction, inspection, troubleshooting & repair of stone veneer walls on buildings, including loose, cracking or bulging stone veneers, water leaks through and behind the stone, waterproofing of stone veneers, and the use of drainage and moisture membranes in stone veneer construction.
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Traditional Stone Veneer Walls on Masonry - loose, falling due to leaks
ur page top photo illustrates very serious damage to what had been a beautiful stone veneer installed on a masonry building at the Mills Mansion in Dutchess County, New York in the U.S.
Lack of maintenance on this building included allowing roof drainage to run down the building wall instead of into a gutter and downspout system.
The combination of water penetration behind the veneer and freezing winter weather have led to the bulge shown at page top, and complete loss of stone veneer and trim in our second photo at left.
This building was a solid masonry stone structure with stone veneer adhered to a rubble-stone wall (shown at left).
Modern Stone Veneer Wall Loose, Bulged, Cracked at Sides
Our stone veneer wall photo (left) illustrates where you can easily spot a stone veneer wall on a modern building and where there is evidence of bulging in the veneer.
This vertical crack between the stone veneer itself and the structural wall behind it is found at building corners (or at garage door openings) where there is a transition between stone veneer and other building wall coverings.
The causes of this cracking and bulging are typically
Omission of proper or an adequate number of fasteners binding the veneer to the building structural wall
Water damage to the stone work or to the structural wall behind it
In some designs, omission of an adequate, supporting ledger at the bottom of the veneer wall intended to help carry its weight.
Repairs of a loose stone veneer may be possible without complete disassembly and replacement, using add-on fasteners that are sold for brick or stone wall veneer retrofit work.
See BRICK VENEER WALL Loose, Bulged for sources of repair connectors for loose masonry veneers.
Modern Stone Veneer Walls - stone over wood framing - leaks lead to rot
This wall looks just fine from outside, but an investigation (of a mold complaint) in the building interior, combined with some strategic test cuts, discovered a history of water leaks behind and through the stone veneer since the time of original construction.
The leaks in this wall originated at the top of the veneer that had not been properly sealed nor flashed at the bottom of the second floor wall and trim (red arrow). We looked for additional leaks around the windows as well (blue arrow).
Mortar between the stone veneer components was also used to "seal" at the veneer-wall top and around the windows where differences in materials (flexibility, rates of thermal expansion) left leaky openings. This house was less than ten years old and had already suffered serious damage.
Water ran down the wall cavity, soaking insulation, rotting sheathing, and leading to a costly mold cleanup job.
Hidden Damage at Leaky Stone Veneers
We took advantage of the extensive building demolition necessary for repair of a home following a fire to take this photo (left) of rot and water stains in the wall cavity of a home similar to the one shown above.
This is the type of damage that occurs at any wood-framed building wall that suffers un-attended leaks for several years or more.
Water had leaked into this wall cavity for more than a decade, leading to rotted sheathing and ultimately, a carpenter ant infestation at the wall sills and lower framing.
Water Leaks at Joints in Stone Veneers on Buildings
Water can leak through a stone veneer wall just about anywhere, even under a roof overhang (photo at left) when a storm produces blowing rain.
Procedures for Installing a Successful Stone Veneer Walls on Buildings
This stone veneer wall (HVFCU, Poughkeepsie, NY) does not appear to have become loose or leaky since installation. Features of a successful stacked stone, fake stone, or cultured stone veneer include: adapting and expanding on advice from Sakrete®:
Fix Leaks in Stone Veneer Walls
I am an indoor air specialist in the Faroe Islands, and I have a stone building with water in between two walls (Sandwich Walls)
I need some literature on the subject, how can i drain these walls from the outside?
There have been ventilation holes, in the outer stone walls in between stones, but they are now sealed, and no ventilation are in between the walls at all.
I have send you pictures from the outside and from the inside of the building.
I hope you can help me. Best Regards, Lone Grønborg, Inniluft Tænastan, Faroe Islands. Email: firstname.lastname@example.org 
Reply: first diagnose the cause of stone wall leaks, second check for hidden damage, third add drainage of proper size and at right location
Thank you for the interesting question - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with moisture trapped in a building wall. That said, here are some things to consider:
It is indeed difficult to construct a stone veneer wall that is waterproof.
For this reason, as with some brick veneer walls (see BRICK WALL DRAINAGE WEEP HOLES) the traditional stone veneer wall is often constructed with a cavity between it and the building structural wall that in turn may be built of wood or masonry. Water that enters the wall is supposed to drain down in the wall cavity and exit at the veneer wall bottom, outside, without entering the building.
Modern stone veneer walls are typically installed without a drainage cavity but over a moisture barrer.
Climate factors for Stone Veneer Walls in the Faroe Islands
Your wall appears to be the first type. Because of your location (the Faroe Islands) your home is probably exposed to severe storms that brew in the North Atlantic, and while you may not be exposed to frost damage in a leaky stone veneer wall, the wall is likely to be exposed to powerful wind-blown rain, making its design and drainage extra important.
Adequacy of original stone veneer wall drainage
Your photo above shows what looks like a small diameter pipe in a stone veneer or stone wall mortar joint at an un-specified height above the wall bottom, but certainly not at the wall bottom. There is no pattern or stain suggesting that this particular opening has been draining water.
Your second stone wall photo (above left) appears to be a test cut opening showing the cavity space between wall cavities.
Diagnose the stone veneer wall leaks first
Before even trying to "drain" water from the wall in your photos we need to accurately diagnose where the water is coming from and how the original wall intended the water to either be kept out or drained from the wall; otherwise your solution may not properly match the problem nor the wall design. Our photos and text above illustrate common leak points in stone veneer wall installations.
Some masonry veneer walls such as a stone veneer over wood framing, are not intended to leak into the structure. Those walls typically lack a drainage system entirely. Leaks in such walls are fixed by finding the points of water entry (say wind blown rain at cracks around stones) and sealing them - a difficult task.
Other veneer walls, such as brick veneer, and some stone veneer walls, perhaps yours, are designed with a cavity between the stone facing and the interior wall, a water barrier over the inner structural wall sheathing, and drainage openings at the wall bottom. Those walls can begin to have a water problem when falling debris in the wall (or insects from outside) block the drain openings.
How to Repair Leaky or Loose Stone Veneers
Carson Dunlop Associates' sketch (left) is of a brick veneer wall, not stone, but the same principles apply to your wall as shown in the masonry veneer shown in the left side of the sketch.
See BRICK WALL DRAINAGE WEEP HOLES for a description of this problem and retrofit products that can be used for additional drain openings.
In general we focus on securing the stone veneer if it's loose, looking for and sealing exterior leaks, and making darn sure that the wall cavity has functional drainage. And we might investigate further for hidden water damage. More dramatic approaches such as wall reconstruction over a water barrer would be an expensive last resort.
For a stone veneer wall such as the one in your photos I would
Watch out for loose masonry veneer that may need repair, replacement, or securing to the structure. (Add-on wall ties to secure loose masonry are also available or can be fabricated if they're not readily available to you. See BRICK VENEER WALL Loose, Bulged http://www.inspectapedia.com/structure/Brick_Veneer_Wall_Loose.php for examples.
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